This invention relates to an operating head for automatic machine tools which uses bevel gear pairs with hypoid crown wheel and pinion to transmit the chuck positioning motion.
In particular, the invention relates to operating heads of the type comprising a fork fitted to a support with several degrees of freedom and a motor chuck, hinged to the fork, which can be revolved and positioned along one or more axes in relation to the fork.
The purpose of the invention is to obtain an operating head of the type indicated above which, though equipped with a high-power motor chuck (5-7 KW), is also very compact, so that work can be performed inside hollow objects if required, and any play due to assembly tolerances and to wear of the parts can be eliminated, and sufficient rigidity is produced to enable the machine to withstand the stresses transmitted by the tool during machining without buckling.
A further purpose of the invention is to obtain an operating head in which, in order to improve the rigidity characteristics of the machine, the head "pivot point" projects less in relation to the chuck connection plane.
Another purpose of the invention is to produce an operating head which is simpler to assemble than the ones currently used.
These purposes are achieved with an operating head in accordance with the characterising part of the claims. Various types of operating head are already known which comprise a fork, fitted to a support with several degrees of freedom, which is equipped with a motor chuck.
For example, U.S. Pat. No. 4,904,131 describes an operating head which presents the general structure described above, in which the chuck positioning motion (axis A) is transmitted from a motor located in the fork support arm to the electric chuck via an inclined shaft with bevel gears at the ends which engage corresponding cogwheels, one built into the fork support arm and the other into the chuck support.
This system produces a very compact head. German patent application no. 3.809.750 also describes an operating head in which the chuck positioning motion is transmitted via a set of bevel gears subject to an axial elastic force, in order to eliminate play due to wear. This system, however, is quite complex and too bulky.
An operating head of the type with fork and electric chuck is also described in Italian Pat. No. 1.220.733, which illustrates a machine tool comprising an arm that moves along three cartesian axes; a fork fitted to the end of the arm can rotate around the arm axis and is equipped with a motor chuck presenting three degrees of freedom in relation to the fork.
These automatic machines are used to perform precision tasks such as milling, contouring, countersinking and other jobs involving the removal of material and assembly work, especially in the aeronautical industry.